Theresa May will today announce plans to tighten the immigration rules, making it easier to deport foreign nationals who have settled and started families in Britain.

The Home Secretary will argue that an over-zealous interpretation of the European Convention of Human Rights (ECHR) is preventing the deportation of illegal immigrants and convicted criminals.

But the crowd-pleasing move, to be announced in her Tory conference speech this morning, will be attacked by human rights and immigrant groups for threatening to split up families and penalise children.

The controversy centres on Article 8 of the ECHR, which provides the right to respect for an individual's "private and family life", but weighs that against the requirement that he or she acts "in accordance with law".

Ms May will tell the Manchester conference that the courts have allowed the fact that a foreign national has started a family to trump the argument that he or she entered Britain unlawfully.

She will announce plans to change immigration rules to make it clear that foreign nationals can be deported even if they have started a family, where they are in the country illegally or have been convicted of a criminal offence.

The new rules will also say they can be removed if they cannot make ends meet, or find a home, without help from the state. A spokeswoman for the Home Secretary said: "It is legitimate to interfere with the exercise of that right where it is in the public interest to do so and in particular where it is necessary for public protection or the economic well-being of the UK, which includes maintaining our immigration controls." Critics of the interpretation of Article 8 point to the cases of a West Indian drug dealer who allegedly beat his girlfriend and a Sri Lankan robber who claimed the right to remain because he had a girlfriend here. Tory sources insisted the moves had been approved by their Liberal Democrat coalition partners, but Nick Clegg's party will be wary of any move that appears to undermine human rights. The Deputy Prime Minister has vowed to block any moves to scrap the Human Rights Act, which enshrines the ECHR into British law.

Kenneth Clarke, the Justice Secretary, will detail plans for his "rehabilitation revolution" in the country's jails. He will spell out plans for "drug free wings" in prisons and to bring in private companies to help inmates kick their habits, paying them by their results.

* Last night Francis Maude, the Cabinet Office minister, accused many prison governors of deliberately tolerating drug use among inmates to keep them placid. It was, he told The Independent's fringe meeting, outrageous that there were fewer offenders with drug problems leaving prisons than entering. "For too much of the prison estate it's the modern equivalent of bromide in the tea," he said.